Impossible to change the notification "applications settings" if emails are disabled

Steps to reproduce:

• go to #xwiki.properties
• disable emails for notifications: #notifications.emails.enabled = false#
• start the wiki
• go to the notification settings
• try to enable/disable the "pages" application
  It fails.
  It actually generates an AJAX request with a bad JSON:

  [
     {
        "eventType":"addComment",
        "format":"alert",
        "enabled":true
     },
     {
        "eventType":"addComment",
        "format":"email",
        "enabled":{
           "length":0,
           "prevObject":{
              "length":0,
              "prevObject":{
                 "0":{
                    "jQuery222075438349066822321":{
                       "olddisplay":"table-row"
                    }
                 },
                 "context":{
                    "jQuery222075438349066822321":{
                       "olddisplay":"table-row"
                    }
                 },
                 "length":1
              },
              "context":{
                 "jQuery222075438349066822321":{
                    "olddisplay":"table-row"
                 }
              },
              "selector":".notificationTypeCell[data-format=\"email\"]"
           },
           "context":{
              "jQuery222075438349066822321":{
                 "olddisplay":"table-row"
              }
           },
           "select…date",
           "format":"email",
           "enabled":{
              "length":0,
              "prevObject":{
                 "length":0,
                 "prevObject":{
                    "0":{
                       "jQuery222075438349066822321":{
                          "olddisplay":"table-row"
                       }
                    },
                    "context":{
                       "jQuery222075438349066822321":{
                          "olddisplay":"table-row"
                       }
                    },
                    "length":1
                 },
                 "context":{
                    "jQuery222075438349066822321":{
                       "olddisplay":"table-row"
                    }
                 },
                 "selector":".notificationTypeCell[data-format=\"email\"]"
              },
              "context":{
                 "jQuery222075438349066822321":{
                    "olddisplay":"table-row"
                 }
              },
              "selector":".notificationTypeCell[data-format=\"email\"]+.notificationTypeCheckbox"
           }
        }
     ]
  

Discovered by Aleksey2610 and confirmed by me:
https://forum.xwiki.org/t/9-11-8-problem-with-turn-on-notification-when-notifications-emails-enabled-false/3969